Ewe mortality rates in the UK are 5-7%; figures that have remained unaltered for the past ten years. Average ewe replacement rates, at 20 per cent, are influenced by longevity and may be compromised by diseases that cause premature death or involuntary culling. Accurate, usually necropsy-based, diagnostic methods for common endemic sheep diseases are well established. Indeed, post mortem examination may be the only reliable method of diagnosis for certain diseases, such as Ovine Pulmonary Adenomatosis (OPA) or to a lesser degree, Johnes disease. Accurate mortality rates for specific diseases are lacking on both a flock and national level, because typically only a minority of sheep carcases are subjected to post mortem examination. If established, such information would enable quantification of the prevalence and cost of each disease and thus inform realistic cost:benefit analyses of interventions aimed at improving flock health.

Project Aims:

Assessment of the diagnostic quality of fallen stock carcases.

Demonstration of the value of post mortem examination of fallen stock to the sheep industry.

Establishment of costs for providing accurate necropsy-based diagnosis of common sheep diseases.

Production of pilot information on the approximate prevalence of ovine diseases, especially those for which there are limited diagnostic tests in the live animal.

Approach:

Ten veterinary pathology sessions were conducted at a fallen stock collection centre, which gathers fallen stock from a large area of northeast England. Each three hour session involved two experienced veterinarians, who examined a random proportion of all available diagnostic ewe carcases, to establish the cause of death. Limited further laboratory diagnostic testing was commissioned where necessary to confirm diagnosis. Agreed minimum diagnostic criteria were used to keep associated costs low.

Results:

The most frequent diagnosis was mastitis, with liver fluke being the next. The full results can be seen in the table below. The pilot project suggested that examination at the centre (gross pathology) was reliable, as around 85% of diagnoses needed no further testing, e.g. histology.

Gross pathology (scour) + Salmonella cultures (2/2) Note: Not considered an adequate cause of death

Dosing gun injury

2

Gross pathology only

Megaoesophagus

1

Gross pathology only

CLA

1

Caseous mediastinal lymphadenopathy + C. pseudotuberculosis cultured

Endocarditis

1

Gross pathology only

Acetonaemia / Fatty Liver

1

Gross pathology + ketonuria

Abdominal torsion

1

Gross pathology only

Chronic nephritis

1

Gross pathology + histopathology

Suspect larval paramphistomum

1

Gross pathology only

Total

106

Although good bacteriology results proved difficult to obtain, this study has shown that it is possible to diagnose the cause of death from fallen stock. It was proposed that the systematic necropsy of fallen stock would improve data on disease incidence, and with appropriate communication back to farmers would encourage good health planning.

Planned activity:

Abstracts were submitted to International Sheep Veterinary Congress and British Society of Animal Science conference. A short communication was published in the Veterinary Record in April 2013. The results will be included in a health and welfare paper submitted to the EBLEX board, plus a report of ewe mortality in England.